1. Field of the Invention
The present invention relates to a tape cassette, and more particularly to a tape cassette comprising a pair of shells made of a synthetic resin material.
2. Description of the Related Art
One general type of tape cassette is an audio tape cassette comprising a magnetic tape wound around a pair of reel hubs and housed in a cassette shell, the magnetic tape having a portion guided by guide rollers and exposed in a front opening defined in the cassette shell. Some cassette tape players that have been available in recent years are of the high-density recording and reproducing type. A cassette tape player of the high-density recording and reproducing type is capable of recording information at high density and with high precision on the magnetic tape in a tape cassette that is loaded in the cassette tape player. If dust particles, fatty deposits, etc. are attached to the magnetic tape, then desired information cannot properly be recorded on and reproduced from the magnetic tape. To prevent such unwanted foreign matter from attaching to the magnetic tape, the tape cassette usually has a lid for covering the exposed portion of the magnetic tape thereby to protect the magnetic tape when not in use.
The tape cassette houses, in addition to tape guide members such as guide rollers for guiding the magnetic tape, a hub brake member for braking the reel hubs to prevent the magnetic tape from being unduly slackened, keep the reel hubs from wobbling, and protect the magnetic tape against damage.
When the tape cassette is loaded into the cassette tape player, the lid is opened, and the hub brake member is slid out of braking engagement with the reel hubs. Hub drive shafts are engaged with the respective reel hubs, and then driven to rotate the reel hubs for thereby transporting the magnetic tape. As the magnetic tape travels, the guide rollers are rotated.
While the magnetic tape is thus moving, desired information is recorded on or reproduced from the magnetic tape by a magnetic head that is held slidably against the magnetic tape.
Tape cassettes of the above structure, particularly miniature tape cassettes, comprising cassette shells and mechanical parts such as hub brake members housed therein, are required to be shaped precisely and be of small thickness. To meet these requirements, they are usually made of polycarbonate resins characterized by precision moldability.
If the cassette shells and mechanical parts are molded of the same synthetic resin, then they tend to adhere to or stick to each other due to the same surface hardness when they slide relatively to each other. As a result, the mechanical parts become highly sluggish, and fail to satisfy operational force ratings which they are required to meet for reliable operation.
In miniature tape cassettes, such an adhesion phenomenon occurs particularly between cassette shells and hub brake members that are held in sliding contact with inner surfaces of the cassette shells. One makeshift solution at present is to apply a lubricant liquid such as a dilute solution of silicon to the inner surfaces of the cassette shells which are contacted by the hub brake members.
However, applying a lubricant liquid such as a dilute solution of silicon to individual cassette shells results in an increase in the number of tape cassette assembling steps and in the cost of assembling tape cassettes. In addition, since it is highly likely for a lubricant liquid to be applied in different ways, e.g., in different concentrations, use of the lubricant liquid is responsible deterioration in quality.